Evidence reported by retrospective investigators and our own prospective studies suggest the existence of psychological factors which precede the clinical appearance of cancer by many years. We obtained an extensive, unique data base (psychological, psychosocial, physiological, medical and familial) on a cohort of 1,337 medical students and have followed them prospectively for 16 to 30 years. New for the most part between the ages of 35 and 59, 55 have already had some type of cancer, and all have reached the age at which the cancer incidence is rising rapidly. It is our aim: a. to study the enlarging cancer group in detail in an attempt to substantiate the youthful psychological characteristics we have already found in this cohort which appear to be potential predictors of cancer: 1) lack of closeness to parents in early life; 2) pathological Rorschach concepts; 3) special keywords in the Rorschach; 4) ambivalent stance of figure drawings. b. to search for new potential predictors of cancer in psychological data not yet examined, including pre-medical school stress data and ratings of their own attitudes and abilities by the students themselves in regard to studying, sports, passive entertainment and active recreation. c. to investigate many parental attributes, psychosocial, habitual and medical, including age and cause of death, in relation to the appearance of cancer in their offspring, the former medical students. d. to determine whether special clusters of predictive variables appear to be associated with particular types of cancer.